Bridging studies in clinical development.

Global development of pharmaceutical products has become the key to the success of any pharmaceutical sponsors. It is therefore crucial to address the efficacy and safety variations of a new test pharmaceutical product among different geographic regions due to ethnic factors. Recently, geotherapeutics has attracted much attention from sponsors as well as regulatory authorities from different geographic regions. To address this issue, the International Conference on Harmonization (ICH) has published a guideline entitled "Ethnic Factors in the Acceptability of Foreign Clinical Data," which is known as ICH E5 guideline. The ICH E5 guideline provides a general framework for evaluation of the impact of ethnic factors on the efficacy, safety, dosage, and dose regimen. We provide an overview of ICH E5 guideline including ethnic sensitivity, necessity of bridging studies, types of bridging studies, and assessment of similarity between regions based on bridging evidence. In addition, challenges on the establishment of regulatory requirements, the assessment of bridging evidence, and design and analysis of bridging studies are addressed.